While the present invention can be effectively used in a plurality of paper-handling or marking systems, it will be described for clarity as used in finisher modules of electrostatic marking systems such as electrophotography. In an electrostatographic reproducing apparatus commonly used today, a photoconductive insulating member may be charged to a negative potential, thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member which corresponds to the image areas contained within the original document. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with a developing powder referred to in the art as toner. During development, the toner particles are attracted from the carrier particles by the charge pattern of the image areas on the photoconductive insulating area to form a powder image on the photoconductive area. This image may be subsequently transferred or marked onto a support surface such as copy paper to which it may be permanently affixed by heating or by the application of pressure. Following transfer of the toner image or marking, the copy paper may be removed from the system by a user or may be automatically forwarded to a finishing station where the copies may be collected, compiled and stapled and formed into books, pamphlets or other sets. This invention will be described throughout in reference to paper collected after the finishing station processes are completed. It should be understood, however, that the present invention can be used in any systems where paper is collected in paper stacks.
As above noted, there are many marking systems that transport paper or other media after the paper is marked in marking step or steps. These marking systems could include electrostatic marking systems, non-electrostatic marking systems and printers or any other system where paper or other flexible media or receiving sheets are transported internally to an output device such as a finisher and compiler station or stations and the subsequent stacking of paper after the compiler completes its functions.
These electrostatic marking systems have finisher and compilers located at a site after the receiving sheets (paper) have been marked with a toner. After finishing is completed, the paper is conveyed to a paper-stacking device generally conveniently located at a bottom portion of the finisher module of a marking machine. A stacking cart generally used is movable so that it can be moved into and out of the finisher module when loaded with paper. Current paper stacking involves the use of carts on casters for compiling paper stacks in printers. Once the carts are loaded, a manual process of unloading small stacks at a time from the main stack is needed. The entire stack cannot be unloaded or staged at once.